МАКРОСКОПІЧНИЙ ТУРБУЛЕНТНИЙ ДІАМАГНЕТИЗМ СОНЯЧНОЇ ПЛАЗМИ

Turbulent motions and convection in cosmic plasma play a key role in the processes of magnetic fields evolution in astrophysical conditions. Involvement of turbulent motions in the consideration, when studying the reconstruction of magnetic fields, ended with the creation of the theory of magnetohydrodynamics of mean turbulent magnetic fields, which in the literature was called macroscopic MHD. One of the important effects of macroscopic MHD is called turbulent diamagnetism. The physical essence of the effect of macroscopic turbulent diamagnetism consists in the displacement of global (mean) magnetic fields from areas of increased intensity of turbulent pulsations to places with less developed turbulence along the gradient of turbulent viscosity gradient νT with an effective macroscopic velocity Uμ = -V̅νT/2 (νT ≈ (1/3)ul, u and l are the effective velocity and the characteristic pulsation scale of the velocity). We considered the role of macroscopic turbulent diamagnetism in the formation of the magnetic field layer in the lower part of the solar convection zone (SCZ). We calculated the radial distribution of the turbulent viscosity νT along the depth z for the SCZ model of Stix (2002). It was found that the radial distribution of this parameter has the form of a convex function νT(z) with a maximum approximately in the middle of the SCZ (z ≈ 140,000 km). Noticeable positive radial gradient of the turbulent viscosity V̅νT, which is found in the lower part of the SCZ, causes a downward intense diamagnetic displacement of the toroidal magnetic field, the velocity of which reaches the value Uμ ≈ 4x103 cm/s near the lower base of the SCZ (z ≈ 180,000 km). Therefore, macroscopic turbulent diamagnetism in deep layers plays the role of negative magnetic buoyancy. Macroscopic diamagnetism acts against magnetic buoyancy, the velocity of which is UB(B) = B/(4πρ)1/2 (B is the magnetic induction, ρ is the density of plasma), and contributes to the formation of a magnetic layer of a steady state toroidal magnetic field with a strength of BS = (4πρ)1/2 νT/2 ≈ 3000–4000 G.